1. Field of the Invention
Aspects of the present invention relate generally to a communication system.
2. Description of the Related Art
When data is transmitted and received via a wireless signal in a wireless digital communication system, information is subject to external distortion and interference due to other wireless signals and Electromagnetic Interference (EMI). In order to recover the wireless signal from the external distortion and interference with high reliability, an error correction coding technique is utilized. Based on a channel code generation method, the error correction coding technique is classified largely into two types of techniques, that is, into algebraic codes such as Bose-Chaudhuri-Hocquenghem (BCH) codes and Reed-Solomon (RS) codes, and bipartite graph codes of tree structures, such as convolutional codes, turbo codes, and Low-Density Parity-Check (LDPC) codes.
The codes of the tree structure feature a relatively simple structure and provide excellent performance for an iterative decoding algorithm, and thus are estimated to be highly appropriate for real-time decoding of high-capacity and high-speed data. However, a Tail-Biting Convolutional Code (TBCC) is adopted as a standard in a great number of communication systems on account of TBCC's simple structure and excellent error correction performance. In a recent Institute of Electrical and Electronics Engineers (IEEE) standard for the 802.16m system, the TBCC is discussed as an error correction code for a control channel. For example, the TBCC is applied to a Secondary Fast Feedback Channel (S-FBCH) and a BandWidth REQuest CHannel (BW-REQCH) of uplink control channels of the IEEE 802.16m system. Convolutional coding is a representative channel coding scheme used to correct errors in many communication systems. Naturally, a lot of standardized modem chips are developed in order to implement the convolutional coding, and the technology is now well developed. Hence, there is a need to develop an algorithm for efficiently decoding the TBCC code using the related-art modem.
The techniques for the decoding of the convolutional code and the decoding of the TBCC code include a survived path search for calculating branch metrics in the trellis, and their respective core operations are generally identical. However, a difference between the decoding of the respective codes lies in that the TBCC decoding determines whether a start state and an end state are identical after the decoding is performed in a trellis diagram. However, a related-art convolutional decoding merely starts the traceback from the zero state, rather than starting the traceback from a maximum path metric. Accordingly, the TBCC coding may not be supported until related-art modem designs are modified so as to decode the TBCC code. Accordingly, a new traceback algorithm for decoding the TBCC code so as to reduce a memory complexity of a decoder for the related-art convolutional code and to reuse core block of the decoder is needed.